This study investigated the electrochemical corrosion characteristics of 347H stainless steel weld joints in a 3.5 wt.% NaCl solution environment. A series of classical electrochemical evaluation methods were employed, including macroscopic and microscopic morphology analysis, open circuit potential measurement, electrochemical impedance spectroscopy, and polarization curve testing. These methods were used to systematically compare and analyze the specific differences in corrosion resistance between two thermal treatment processes—solution treatment and stabilization treatment—and between the weld zone and the base metal. The results showed that both solution treatment and stabilization treatment can significantly enhance the corrosion resistance of 347H stainless steel material. Moreover, under the same thermal treatment, the weld zone is less prone to corrosion than the base metal area.